This blog provides updated forecasts and comments on current weather or other topics

Saturday, January 5, 2013

Gulf of Alaska Storms Versus Shell Oil Drilling Platform

The storms win.

Shell Oil made a misguided and poorly informed decision to move a huge drilling platform (the Kulluk) from Dutch Harbor Alaska to Seattle starting December 21st. As described in the Seattle Times and elsewhere the problems grew from broken tow lines and faulty engines on December 26th, to the eventual grounding the Kulluk on an island just south of Kodiak island on December 31st.

The Kalluk beached south of Kodiak Island

Anyone familiar with the meteorology of the North Pacific and the Gulf of Alaska knows that this region is one of the stormiest on the planet with one major storm after another during midwinter. Unbelievably, a Shell Oil spokesman said, that forecasts indicated a favorable two-week weather window. This is at odds with the facts. First, as I will show below the forecasts on the day they left clearly suggested the potential for big storms during the 3-4 week voyage to Seattle, including the first week. Second, forecast skill drops substantially after 4-6 days and thus there was no guarantee of fair weather for this difficult tow.

Lets take a look at the surface charts during a few points in this ill-favored trip.
First, chart of 10am on the 26th, when wind conditions and large seas caused them to have lots of problems with tow lines. A 960 hPa low is found southeast of Kodiak; keep in mind this is about the same central pressure of the Columbus Day Storm, perhaps the greatest storm to hit Seattle during the past century. Such storms are a dime a dozen in the Gulf!

Then 10 AM on the 28th. Two major cyclones..one with 962 hPa and the other around 967 hPa to the southwest.

And then at 4 PM on December 31st, the coup de grace--a 959 hPa storm the produced very strong easterly winds over Kodiak and large (up to roughly 40 ft) seas.

Folks, a sequence like this is not unusual this time of the year and any experienced Pacific mariner knows it.

Were these storms big surprises as claimed by Shell? Let me show you some forecast model output and you decide! The University of Washington forecasts over the Pacific are virtually identical to that of the main U.S. global model, the model used heavily by the National Weather Service to forecast conditions over the Pacific. I have easy access to the graphics, so lets look at them. The tow began on 21 December, so lets examine the forecast started at 4 PM Seattle Time (3 PM Kodiak Time) valid at 4 PM on December 26th. A strong 967 hPa low south of the Aleutians. Not bad five days ahead of time...and of course the subsequent forecast got even better. Clear warning that the tow was a bad idea.

So there they were on December 26th and in trouble. You would think they would check the forecast to see whether they should head to port. So lets looks review the 5 day forecast for 31 December at 4 AM. ANOTHER strong storm...even deeper... with Kodiak Island in the area of strong pressure differences and thus strong winds.

I should note here that forecasts over the oceans have gotten much more accurate during the past decade or so, the key reason being the huge amount of satellite data we get over the oceans these days. In the old days we used to get a lot of observations in the middle of storms as storms got caught due to the poor forecasts. Today they avoid the storm!

Ok, that is one forecast. State-of-the-art forecasters use ensembles (the output of many model runs) that can give us uncertainty information and a measure of the confidence of the forecasts. One of the most popular ensembles collections used by U.S. forecasters is NAEFS...the North American ensemble system that combines the ensembles of both the U.S. and Canadian ensemble system. Here is the output from this system for the runs started at 4 PM on 26 December for the town of Kodiak. Look at the wind speed panel (note the wind speeds are given in km per hour, e.g., 40 km per hour is 25 mph). The bracket shows the range of speeds from the various ensemble members and the middle bar is the median). Clearly, some of the solutions are for very wind conditions.

The bottom line is that based on climatology and the forecasts available throughout the period, this was no time to be doing a very difficult tow over the northern Gulf of Alaska. We should expect more from a major international company that is being trusted to drill for oil in ecologically sensitive regions.

Hi Cliff,Having spent my last 2 years of my 20 years in the Coast Guard up in Alaska patrolling this very area, I understand it all too well. There really is no "window of good weather" this time of year up there. Reading about Dutch Harbor and Kodiak brought back some really fond memories. Thanks for that and as always an informatively great read!

I wonder where the forcaster was for this. So much forecasting these days is done from hubs in another part of the country or even the other side of the world. Nothing is as good as being there. Shell should have talked to the wx office in Kodiak or Juneau.

while back, you guys took air particulate measurements during passage of coal trains along puget sound. never saw the results of that little study.

just a heads up, i read that BNSF is now conducting their own study in order to combat "environmentalists" in the PNW. they are installing testing equipment on coal trains in Laurel MT headed to the PNW. dont know many more details.

I wonder if their forecaster told the higher-ups something like "pretty typical weather for this time of year, which means storms every day or two" and the suit turned it around "okay, typical weather, nothing abnormal we're good to go!"

Great coverage Cliff! Rachel Maddow did a good piece on her Friday show about the Kulluk and interviewed Popular Mechanics deputy editor Jerry Beilinson who was on the rig in October, about the decision to move it this time of year. It sounds like there's a possible federal investigation in the making - maybe you could lend your expertise!

"You would think the decision-makers at Shell would have had some input from the tug captain and others familiar with the area."

They did get local input - the most respected salovor (marine recovery specialist) in Alaska told them his firm was not willing to participate in the adventure. He gave them the same weather info that Dr Mass describes.

The largest marine towing company in Alaska also refused to participate and told them a tow, at any time of the winter, across the Gulf of Alaska was a foolish and dangerous exercise.

the commercial marine captains forum gcaptain has a great open discussion about these issues